1. Field of the Invention
The present invention relates, in general, to a toothbrush having needle-shaped bristles, in particular, to a toothbrush having needle-shaped bristles which has improved in terms of the teeth and gum contact force as well as the teeth cleaningperformance and has a prolonged lifespan.
A needle shaped bristle refers to a bristle having an end point with a diameter of 0.01 to 0.08 mm. Needle-shaped bristles are commonly used as the material for high quality toothbrushes because they are soft and the force with which they contact the area between a tooth and a tooth or between a tooth and a gum is excellent.
Despite of the advantages described above, disadvantages of the toothbrush having the needle-shaped bristles include insufficient tooth cleaning performance and a short lifespan. The toothbrush has additional disadvantages such as a high error rate and a high production cost because two soaking processes are required to taper both end portions of a bristle.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Various methods have been attempted to solve the problem of the toothbrush having the needle-shaped bristles discussed above. Toray Industries Inc. of Japan has attempted to solve this problem by setting half-folded bristles of which one side is tapered and the other side is not tapered (Japanese Utility Model Application Laid-Open No. Sho. 61-10495). Although this technology eliminates some of the drawbacks of the toothbrush having the needle-shaped bristles, it creates the new problem of the sharp cut edge of the non-tapered bristles hurting the gums during brushing of the teeth.
Korean Patent No. 10-0590608 discloses a technology for solving the above-discussed problem, and was invented by the present inventors. This technology solves the above-discussed problem by using a manner of grinding the sharp cut edge of a bristle with a grinder, tapering the opposite side of the bristle with chemicals, and then setting the bristle. This technology has solved the problems of the above-mentioned technology, but the obtained toothbrush still has the problems of the force of contact with the teeth and gum being slightly insufficient and an additional grinding process being required.
In Korean Registered Utility Model No. 20-0308084, needleshaped bristles having an equal taper length and an equal diameter at their end points are asymmetrically set so that left and right sides of the bristles have a deviation in height. With this setting, the teeth and gum contacting force is slightly improved, but the cleaning performance is still insufficient. In addition, thus obtained toothbrush still has problems of the lifespan being shorter than that of the toothbrush having general needle-shaped bristles, and the error rate remaining high because two soaking processes are still required.
Japanese Patent Application Laid-Open No. Heisei. 10-225324 introduces a toothbrush where both ends of each bristle have different taper lengths, and the bristles are set in such a manner that the part of the bristle with the longer taper length is used as a longer bristle and the part of the bristle with the shorter taper length is used as a shorter bristle. This technology slightly improves the teeth and gum contact force, but still has the same problem as does the general toothbrush having needle-shaped bristles because it uses bristles having an equal diameter of the end point. There is another meaningful conventional art related to a toothbrush having needle-shaped bristles, which is Korean Patent No. 10-066457 invented by the present inventor, in which the process of tapering bristles is performed by grinding with a grinding stone having projections without using a chemical immersion process so that the burdensome chemical immersion process can be eliminated. According to the technology, the bristles can be tapered by a physical method. In addition, bristles made of nylon or acryl, which are difficult to taper in the conventional art, can be tapered according to this technology.
The-above discussed technologies are far removed from a toothbrush having a long lifespan and having both the teeth and gum contacting force and the teeth cleaning performance being improved. Among the technologies, the technology which is the closest to the object of the present invention is described in Korean Patent Application No. 10-2003-0015480 invented by the present inventors of this invention.
This technology relates to a toothbrush having longer needle-shaped bristles and shorter needle-shaped bristles both set on the head portion of the toothbrush, and also relates to a toothbrush in which needle-shaped bristles having taper lengths of 3 to 7 mm and end-point diameters of 0.01 to 0.07 mm are set on the head portion in a mixed manner so that bristles are half-folded so as to have a deviation of 0.5 to 2.0 mm between left and right sides and be set on the head portion of the toothbrush. In this manner, most of the objects of the present invention have been achieved, but this technology is still slightly unsatisfactory in terms of the teeth and gum contact force, teeth cleaning performance, and the effect of prolonging the lifespan.
Another method is disclosed in Korean Patent No. 10-0659953 presented by Lion Corporation of Japan. According to the method, provided is a toothbrush using monofilaments in a tapered form where the diameter of the monofilament at a position 0.1 mm from the tip of a tapered portion is 5 to 35% of the maximum diameter (D) of the synthetic monofilament. The toothbrush according to the technology has the same end point on the both sides, and the length of the tapered portion is 8 5 to 15 mm, and preferably 8 to 10 mm. Accordingly, the toothbrush has a short lifespan and lacks teeth cleaning force because the length of the tapered portion is too long. Therefore, the toothbrush is suitable for use as a paint brush or a cosmetic brush, but it is not suitable for use as a toothbrush.